The present invention relates to a manufacturing method for a bottle-shaped can, of which a can body, a shoulder portion and a neck portion are integrally shaped from a metallic sheet (or a metal sheet), and, more particularly, to a method of manufacturing a bottle can with the outer surface of its body portion or the outer surface of the portion from its body portion to its shoulder portion being decorated with a print or the like.
As beverage cans for various soft drinks, juice or beer, there are generally employed the two-piece cans, of which the can body (or side wall portion) and the can bottom (or end wall portion) are integrally shaped. The two-piece can of this kind is manufactured by a suitable method such as by drawing and ironing, by drawing/redrawing, or by drawing/redrawing and stretching a metallic sheet such as an aluminum alloy sheet or a surface-treated steel sheet.
In such a two-piece can, there are integrally shaped the can bottom having a domed shape for improving the pressure resistance and the thinned body portion, and the open upper end portion of the body portion side wall is necked in to reduce the diameter and is flanged.
Moreover, the two-piece can is filled with a body such as a juice, soft drinks or beer, and the flanged portion of the open body portion is then seamed and sealed with an easy open can end having a smaller diameter than the external diameter of the body portion so that the can is shipped as a beverage can.
This beverage can is opened by a consumer having purchased it when the consumer pulls a tab fixed on the easy open can end.
As disclosed in WO 81/01259, on the other hand, there is also manufactured a bottomed cylindrical can which is shaped to have a thinner body wall than a bottom wall by drawing and redrawing (or by bending and extending at the redrawing time or by stretching) the surface-treated steel sheet having two sides laminated with a thermoplastic resin film. The can thus manufactured is necked in and flanged like the aforementioned can so that it may be used as the beverage can.
As the containers for soft drinks, juices, teas or coffees, on the other hand, there have been employed in recent years the bi-oriented molded containers (i.e., the PET bottle) made of a polyethylene terephthalate resin. Accordingly, the various soft drinks and others contained in the re-sealable PET bottles are mass-produced and sold by filling the bottles with them and by sealing the bottles with the threaded caps.
These beverage PET bottles have an advantage over the can containers for the beverages in that they can be repeatedly sealed with the caps. However, the PET bottles are in considerably lower states than those of the can containers in the recycling ratio for recovering and recycling the bottles. Therefore, it has been investigated to enhance the conveniences of the can containers by adding to the re-sealing function to the can containers having a high recycling ratio.
As the metallic cans which can be re-sealed with the threaded caps, there are disclosed in Japanese Patent Laid-Open No. 10-509095 (WO96/15865) several types of bottle-shaped drawn/ironed cans (i.e., DI cans) having shapes similar to those of the PET bottles, i.e., the DI cans which have threaded neck portions to be screwed with threaded caps.
These DI cans are classified into: the type in which an end sheet to be seamed on the open upper end of a can body is formed to form a threaded neck portion integrally; the type in which the threaded neck portion is integrally formed by reducing the diameter of the open upper end side of the can body stepwise by the neck-in working (i.e., by making the diameter smaller toward the open end); and the type in which the small diametrical neck portion and the shoulder portion having a slope are formed by drawing the drawn bottom E portion side (or the end wall portion) of a cup at multiple steps, in which the neck portion is then opened and is curled and threaded, in which the body portion of the cup is then drawn and ironed into a thin body portion, and in which a separate bottom end is seamed and fixed on the open end of the body portion on the side opposed to the neck portion.
In the above-specified Laid-Open, moreover, there are disclosed not only the structures of the bottle-shaped cans of the individual types but also their shaping (or forming) methods.
According to the disclosure of Japanese Patent Laid-Open No. 58-47520, on the other hand, at the time of drawing the can body, the bottom portion is drawn into a convex stepped shape, and this convex stepped shape is redrawn at an ironing time, to form a stepped convex portion having a small diametrical cylindrical neck portion and a raised shoulder portion. This neck portion is threaded and is sealed with the threaded cap. After this DI can was filled with a beverage from the end opening of the body portion, this end opening is sealed by seaming and fixing the can end.
In Japanese Patent Laid-Open No. 64-47520, moreover, the following concept is disclosed. By pressing (or drawing) the bottom side of the DI can shaped by the drawing/ironing treatment, there are shaped a small diametrical cylindrical neck portion and a frustoconical shoulder portion. The leading end portion of the neck portion is trimmed, and the lubricant having stuck the inner and outer surfaces of the can is degreased/rinsed. The inner and outer surfaces of the can are conversion coated and dried. After this, a coating for the inner surface is sprayed on the inner surface of the can. After the coating is dried, a print is applied to the outer surface of the body portion of the can. After this printing ink is dried, a can end is seamed and fixed on the open end of the body portion. After this, a threaded cylindrical member of a resin is fitted on the neck portion, or this neck portion is screw-cut.
Of the aforementioned bottle-shaped cans which can be sealed again with the threaded cap, the can of the type in which the threaded neck portion is formed integrally with the end sheet is formed at its body into the DI can or a bottomed can such as the DTRD can (Drawn Thin Redrawn) having been drawn and bent/extended (or stretched) or the can having been drawn and bent/extended (or stretched) and ironed. The can body is filled with a content such as a beverage, and the open end portion of the can body is seamed/fixed and sealed with the end sheet having the threaded neck portion formed integrally therewith.
According to the bottle-shaped can of this type, therefore, the can body has a shape substantially identical to that of the existing general can, and enjoys an advantage that few changes are required in the filling facilities to suppress the cost for the facilities.
In the bottle-shaped can of this type, however, the end sheet seaming portion is located in the upper portion of the can to raise problems that dust is liable to accumulate in the concave portion inside of the seamed portion, and that the seamed portion itself protrudes to deteriorate the appearance.
In the bottle-shaped can of the type in which the neck portion is formed not at the end sheet but integrally at the upper end portion of the can body, on the other hand, the upper end portion is stretched thin and worked hard by a similar working as the can body is drawn and ironed or bent and extended. Considering the later step of working the neck portion, therefore, the upper end portion of the can body is worked so relatively thick as to make the extension of the material less than the lower portion (or as to reduce the work hardening extent).
Since the neck portion has a considerably smaller diameter than that of the can body (or the body portion of the can), however, a diameter reduction ratio for forming the neck portion is so large as to make it necessary to make a diameter reduction work many times.
When the number of the diameter reduction work is reduced by enlarging one drawing rate, on the other hand, the can body is wrinkled or cracked at its upper end portion.
In order that a small cap may be used to lower the cost for the material and that the consumer may drink the beverage in the can directly from the neck portion without spilling the content, it is desired to reduce the diameter of the neck portion more than the external diameter of the can body.
In order to satisfy these desires, it is necessary to make the reduction ratio higher for forming the neck portion by drawing the open upper end of the can body, and this necessity requires several tens of neck-in steps.
For example, the can to be relatively frequently used as the body can for beer has a body diameter of about 66 mm (the so-called xe2x80x9c211 diameterxe2x80x9d), and twenty to thirty necking steps are required if the neck portion of such can is to be necked in to a diameter of about 28 mm.
Thus, in the bottle-shaped can having the neck portion formed by reducing the diameter of open upper end of the can body, a number of necking machines are required to raise the cost for the facilities, and the increase in the number of working steps makes it frequent to damage or deform the can thereby to lower the quality of the can.
In the bottle-shaped can of the type in which the shoulder portion and the neck portion are formed by working the can bottom, on the contrary, the can bottom portion or the portion to be formed in a portion of the shoulder portion and the neck portion is hardly affected by the working to form the can so that the working is applied to the portion having no work hardening and having a thickness substantially equal to that of the original metallic sheet. When the can bottom is to be drawn, moreover, the diameter of the neck portion can be reduced while being unwrinkled.
As compared with the case in which the neck portion is formed by necking in the upper portion of the aforementioned can body, therefore, one drawing rate can be increased to reduce the diameter more by one step thereby to drastically reduce the number of steps for forming the neck portion.
On the other hand, the bottle-shaped can of the type in which the bottom side is worked to shape the shoulder portion and the neck portion has neither a seamed portion at its upper portion nor a recess liable to trap dust while the can is displayed at a store front, so that it has an excellent appearance.
Here in the aforementioned bottle-shaped can which has its neck portion, shoulder portion and body portion shaped integrally so that it can be re-sealed with the threaded cap, a protecting coating film is applied to the metallic surface of the can so as to protect the content and retain the corrosion resistance. If the metallic sheet is then pre-coated with the protecting coating film, this film is damaged when the can is ironed. It is, therefore, disclosed in Japanese Patent Laid-Open No. 10-509095 that the protecting coating film is formed after the ironing treatment.
In Japanese Patent Laid-Open No. 58-47520, on the other hand, it is not disclosed in the least when the protecting coating film is applied, when the small diametrical cylindrical portion is cut and opened or when the same is threaded.
According to the disclosure of Japanese Patent Laid-Open No. 64-47520, on the other hand, a bottomed cylindrical can body having a thin body portion is shaped by the drawing treatment and the ironing treatment. After this, the can body is drawn at its bottom portion to shape a small diametrical cylindrical portion and a frustoconical shoulder portion. After the upper end portion of the small diametrical cylindrical portion is cut and removed, a degreasing treatment is performed to rinse the inner and outer surfaces of the can body, and this body is dried. A protective coating is then applied to the inner surface of the can body and is dried. After this, a print is applied to the outer surface of the can body.
According to our experiences, however, it is seriously difficult to apply a protective coating of a uniform thickness to the metal surface of a can (before the bottom end is fixed) having the curled portion or the threaded portion formed at the small diametrical neck portion and to dry and set the coating to a proper state.
According to the shaping method utilizing the ordinary DI can manufacturing method, on the other hand, a cup of a metallic sheet having a surface laminated with no thermoplastic resin is redrawn and ironed while spraying much water lubricant to the cup. Therefore, much degreasing liquid, conversion coating liquid and rinsing water is required for the rinsing treatment. This makes it necessary to employ large-sized rinsing facilities and the much lubricant, degreasing liquid, conversion coating liquid and rinse water. This necessity is a factor to raise the can manufacturing cost drastically.
In order to simplify the degreasing treatment after the can body is shaped, therefore, we have adopted the following method. A thermoplastic resin film layer performing a function as the lubricant is formed in advance as the protective film on the metallic sheet for the material of the can, and a small amount of lubricant is applied to the protective film. The coated metallic sheet thus having the protective film is shaped into an integral structure of a thin body portion, a shoulder portion and a neck portion. After this, the neck portion is shaped to have a curled portion and a threaded portion.
The bottle-shaped can thus manufactured from the coated metallic sheet need not be coated later for protecting it. If a high-temperature volatile (or sublimable) lubricant is employed, the degreasing treatment can be simply effected by a heating treatment. Even in the case of a non-high-temperature volatile lubricant, on the other hand, the degreasing treatment can be effected with a small amount of rinse water.
Where a print of letters or decorative patterns is to be applied to the body portion of a container, the PET bottle can not be printed directly on the entire circumference of the bottle body, or a printed resin film cannot be fusion-bonded as a matter of fact, because its body portion is not circular, corrugated or extremely thin. Therefore, the print is applied by shrink-packaging the bottle body with a printed heat-shrinkable film.
In the metallic bottle-shaped can of the type in which the threaded neck portion, the shoulder portion and the body portion are integrally shaped and in which the bottom end is seamed and fixed on the lower end portion of the body portion, an opening of the same external diameter as that of the body portion is kept till the neck-in step before the bottom end is fixed. It is, therefore, possible to print the can body directly as in the two-piece can of the prior art and to thermally adhere (or fusion-bond) the printed resin film. Thus, an appearance different from that of the PET bottle can be obtained to differentiate the products.
Even where the body portion, the shoulder portion and the neck portion of the metallic bottle-shaped can are to be integrally shaped from the coated metallic sheet having the protective film, however, this protective film may be damaged by the friction at the shaping time by the drawing or ironing treatment, unless the lubricant is applied in advance to the surface of the coated metallic sheet. Where the decorative print is to be applied to the body of the bottle-shaped can, on the other hand, it is made impossible from the view points of the repellency of the ink or adhesiveness to directly print the outer surface of the can in the state having the lubricant or to fusion-bonding the printed resin film to the same. Therefore, it is a problem what stage (time) of the manufacture process is most suitable to the printing (or the fusion-bonding of the printed resin film).
In the aforementioned Japanese Patent Laid-Open No. 58-47520, there is no disclosure at what point of time the decorative print should be applied.
In the aforementioned Japanese Patent Laid-Open No. 64-62233, on the other hand, the following is disclosed. After the bottomed cylindrical can body is drawn at its bottom side to shape the small diametrical cylindrical portion and the frustoconical shoulder portion, the upper end portion of the small diametrical cylindrical portion is cut and removed. After this, the can body is rinsed at its inner and outer surfaces and is dried. After this, the coating is sprayed on the inner surface of the can body. After the coating is dried, the coating and the print are applied to the outer surface of the can body.
According to the manufacturing method for the bottle-shaped can body, as disclosed in that Laid-Open, the coating is sprayed on the inner surface of the cylindrical can body after this can body is drawn at its bottom portion to form the small diametrical cylindrical portion and the frustoconical shoulder portion.
It is, however, not easy to apply the protective coating of a uniform thickness to a body having portions of different diameters combined, such as the inner surface of the bottle-shaped can body after the cylindrical body portion, the frustoconical shoulder portion and the small diametrical cylindrical portion are formed.
For coating the inner surface of an article having such complicated shape, more specifically, the spray coating is commonly used, as disclosed in that Laid-Open. However, the coating film is liable for the spray coating to become thick at a small diametrical portion but thin at a large diametrical portion. Therefore, a coating consumption is excessively high if a sufficient application is to be retained for the thin portion, and a coating film thickness for retaining a sufficient corrosion resistance cannot be obtained if the coating consumption is limited.
Where the coating film thickness on the inner surface of the bottle-shaped can is seriously different at portions, on the other hand, the drying degree disperses when the coated film is dried/baked. Therefore, sufficient corrosion resistance and adhesion may not be able to be obtained to make the drying/baking works difficult.
In the bottle-shaped can body manufacturing method disclosed in the Laid-Open, moreover, the can body is printed on its outer surface after the small diametrical cylindrical portion for the threaded neck portion is cut/removed at its upper end portion (or its leading end portion). If, in this case, there is diverted the dry offset printer which is employed for printing the ordinary two-piece can (e.g., the DI can or the deeply drawn can), this diversion is impossible unless a drastic modification is made. This raises a problem that the cost for the facilities is raised.
In Japanese Patent Laid-Open No. 10-509095, there is disclosed the bottle-shaped can in which the body portion, the shoulder portion and the small diametrical cylindrical portion are integrally shaped. The cup, as adapted by the drawing treatment, is shaped to form the small diametrical cylindrical portion and the shoulder portion. After this, the small diametrical cylindrical portion is cut and opened at its leading end portion. After this, the small diametrical cylindrical portion is curled and threaded at its leading end portion. Moreover, the cup is redrawn and ironed to elongate the can body wall and is coated for the protection. Therefore, the problem of the bottle-shaped can disclosed in Japanese Patent Laid-Open No. 64-62233 is just as the same as that of the bottle-shaped can of the aforementioned type, as disclosed in Japanese Patent Laid-Open No. 10-509095.
In the prior art in which the two-piece can is directly printed at its cylindrical body portion or in which the printed resin film is fusion-bonded to the body portion of the two-piece can, as disclosed in Japanese Patent Laid-Open No. 9-295639 (corresponding to EP-A2-0,808,706), the transfer means employed for feeding/discharging the cans to the mandrels or the like of a printing apparatus or a printed resin film applying apparatus is exemplified by the transfer means utilizing the vacuum and compressed air injection Glmechanism (as disclosed in Japanese Patent Laid-Open No. 48-58905 (corresponding to U.S. Pat. No. 3,766,851), Japanese Patent Laid-Open No. 52-41083 (corresponding to U.S. Pat. No. 4,048,917), U.S. Pat. No. 4,092,949, Japanese Patent Laid-Open No. 54-92810, Japanese Patent Laid-Open No. 57-170758 or Japanese Patent Laid-Open No. 57-178754).
For the printing of the bottle-shaped can body disclosed in Japanese Patent Laid-Open No. 64-62233 or Japanese Patent Laid-Open No. 10-509095, the transfer means utilizing the vacuum and compressed air injection mechanism cannot be used at the printing time when the bottle-shaped can body is to be fed to and discharged from the mandrels of the printing apparatus, because an opening is present at the leading end portion of the small diametrical cylindrical portion in addition to the opening at the leading end of the body portion.
It is, therefore, necessary to add a mechanism for grasping and pushing the bottle-shaped can body reliably on the mandrels of the printing apparatus and a mechanism for grasping and removing the bottle-shaped can body reliably from the mandrels. As a result, those modifications to the printing apparatus raise a problem that high expenses are required for the facilities to raise the cost considerably for manufacturing the can.
Since the bottle-shaped can body is grasped for its transfer, on the other hand, there arises another problem that the transfer rate is reduced to have a low printing speed.
A main object of the invention is to provide a method for manufacturing such a re-sealably threaded bottle-shaped can at a low cost that a small diametrical neck portion, a shoulder portion and a large diametrical body portion are integrally molded from a metallic sheet (or a metal sheet), that a homogeneous protective film is applied to the inner surface of this portion, and that a decoration print is applied at least to the body portion.
A more specific object of the invention is to provide a manufacturing method for a re-sealably threaded bottle-shaped can, in which no protective coating is needed on the inner surface of the can after manufactured and in which the decoration print can be applied to the body portion without any drastic modification on the decorating apparatus of the prior art for the outer surface of the body portion of the two-piece can.
In order to achieve the above-specified objects, according to the invention, there is provided a manufacturing method for a bottle-shaped can in which a small diametrical neck portion, a shoulder portion having a sloped face and a large diametrical body portion are integrally shaped, in which a decoration print is applied at least to the outer surface of the body portion and in which a bottom end is fixed on the lower end portion of the body portion, comprising: a cup shaping step of preparing a covered metallic sheet, by forming thermoplastic resin coating films on the two surfaces of a metallic sheet and by applying a lubricant to the thermoplastic resin coating films, and punching out the covered metallic sheet to form a cup shape; a can shaping step of shaping the shaped cup further into a bottomed cylindrical can which is reduced at diameter of the body and thinned at its body portion; a diametrical small cylindrical portion shaping step of shaping the bottom portion of the bottomed cylindrical can and the body portion in the vicinity of the bottom portion into the shoulder portion and an unopened small diametrical cylindrical portion; an opening step of cutting and opening the leading end portion of the small diametrical cylindrical portion; a neck portion shaping step of shaping the neck portion by threading the outer circumference of the opened small diametrical cylindrical portion; a lubricant removing step of removing the lubricant from the outer surface of the bottomed cylindrical can, between the step of shaping the bottomed cylindrical can having the thinned body portion and the step of cutting and opening the leading end portion of the small diametrical cylindrical portion; and a decorating step of decoratively printing the outer surface of the body portion of the bottomed cylindrical can cleared of the lubricant, between the step of shaping the bottomed cylindrical can having the thinned body portion and the step of cutting and opening the leading end portion of the small diametrical cylindrical portion.
According to the bottle-shaped can manufacturing method of the invention, therefore, the metallic sheet still in the flat state before shaped is laminated in advance on its two surfaces with the thermoplastic resin so that the thermoplastic resin as the protective film can be applied in the uniform thickness to the metallic sheet surfaces. Since the small diametrical cylindrical portion (or the neck portion), the shoulder portion and the body portion are integrally shaped from the coated metallic sheet (i.e., the metallic sheet with the protective film) prepared by applying the lubricant to the thermoplastic resin layer, on the other hand, the protective film for protecting the metallic sheet of the can is not damaged at the step of shaping the small diametrical cylindrical portion, the shoulder portion and the body portion integrally. Since the protective film is formed of the thermoplastic resin layer, moreover, this thermoplastic resin layer not only functions a lubricant fi when the small diametrical cylindrical portion (or the neck portion) is bent or threaded after the lubricant is removed but also is extended or bent following the extension or bend of the metallic surface, so that protective film does not peel off.
In short, no protective covering need be applied to the inner surface and the outer surface of the shaped can. As a result, there is raised neither such problems in the coating workability or in the irregularity of the thickness of the protective film as might otherwise occur where the coating is sprayed to the inner surface of the can after made.
According to the bottle-shaped can manufacturing method of the invention, on the other hand, the step of removing the lubricant from the body portion of the can and the step of printing the decoration are performed after the bottomed cylindrical can having the thinned body portion is shaped and before the small diametrical cylindrical portion is cut and opened at its leading end portion. By employing the transfer means according to the vacuum or compressed air injection mechanism which the printing apparatus or the printed film resin film adhering apparatus of the prior art is equipped with, therefore, the bottle-shaped can can be fed to and discharged from the mandrels of the printing apparatus or the printed resin film adhering apparatus. Therefore, the decoration step can be effected at a high speed.
In the bottle-shaped can manufacturing method of the invention, on the other hand, the step of printing the body portion of the can or adhering the printed resin film is performed after the lubricant removing step so that the printing operation or the printed resin film adhering operation can be performed in a satisfactory state.
In the method of the invention, on the other hand, the lubricant removing step and the decoration step may be executed between the small diametrical cylindrical portion shaping step and the opening step.
In the bottle-shaped can manufacturing method of the invention, therefore, the shoulder portion and the small diametrical cylindrical portion are shaped before the lubricant is removed, so that these shaping steps are performed with the lubricant being left on the thermoplastic resin layer. It is, therefore, possible to perform the numerous steps of shaping the small diametrical cylindrical portion and the shoulder portion while preventing the thermoplastic resin film from being damaged.
In the bottle-shaped can manufacturing method of the invention, on the other hand, the bottle-shaped can at the instant when it is fitted (or crowned) on the mandrels of the printing apparatus or the printed resin film adhering apparatus has a small diametrical cylindrical portion formed on its bottom portion. By the modifications that the mandrel is partially matched to the shape of the shoulder portion of the can and that the inner surface of the vacuum pad for sucking the can is partially matched to the shape of the shoulder portion shape of the can, however, the vacuum and compressed air injection mechanism can be employed when the can is to be fed to and discharged from the mandrel. Therefore, it is possible to suppress the cost for the modifications.
In the method of the invention, still moreover, the lubricant removing step and the decoration step may be executed between the can shaping step and the small diametrical cylindrical portion shaping step, and a lubricant applying step of applying a lubricant at least to the outer surface of the bottomed cylindrical can may be executed immediately after the decoration step.
In the bottle-shaped can manufacturing method of the invention, therefore, at the stage where the bottomed cylindrical can is shaped, the lubricant is removed, and the decoration print is applied to the outer surface of the cylindrical body portion. Therefore, the printing apparatus or the printed resin film adhering apparatus, as has been employed for printing the body portion of the two-piece can, can be employed without any modification.
In the bottle-shaped can manufacturing method of the invention, on the other hand, after the body portion is printed, the lubricant is applied to the bottle-shaped can, and the can bottom portion including the vicinity of the bottom portion of the printed body portion is shaped into the shoulder portion and the small diametrical cylindrical portion. It is, therefore, possible to manufacture the can in which the decoration print is applied at least to such a portion of the shoulder portion of the bottle-shaped can as can not be decoratively printed by the ordinary printing means.
Still moreover, the small diametrical cylindrical portion shaping step of the method of the invention may be executed: such that the bottomed cylindrical can is preliminary molded at its bottom corner portion into a curved shoulder face having an arcuate longitudinal section and is then drawn at its bottom portion into a bottomed cylindrical portion of a smaller diameter than that of the body portion while the curved shoulder face of the bottom corner portion being unwrinkled by a pair of unwrinkling pusher and drawing dies having curved faces to contact closely with the curved shoulder face; such that after this, an unwrinkling pusher, which is provided at its leading end portion with a tapered face having a substantially straight longitudinal section approximating a tangential line drawn to an arcuate longitudinal section of a virtual curved face leading to a preformed curved shoulder face, a redrawing dies, which is positioned at a portion to face at least the unwrinkling pusher and which is provided at its leading end portion with a tapered face having a substantially straight longitudinal section approximating a tangential line drawn to an arcuate longitudinal section of a preformed curved shoulder curved face, and a redrawing punch are used to perform one or more redrawing treatments for reducing the diameter of the bottomed cylindrical portion, while the bottom corner portion of the bottomed cylindrical portion of the small diameter formed by the drawing treatment being unwrinkled, thereby to shape the bottomed cylindrical portion of the small diameter into a small diametrical cylindrical portion of substantially the same diameter as that of the neck portion; and such that after this, one or two or more continuing tapered faces formed between the small diametrical cylindrical portion and the curved shoulder face are extended and re-shaped into a smooth curved face leading to the curved shoulder face by a pair of re-shaping tools having a surface shape of a virtual curved face extending from the curved shoulder face, to form the shoulder portion into a curved face of a domed longitudinal section.
According to the bottle-shaped can manufacturing method of the invention, therefore, it is possible to manufacture the bottle-shaped can which is provided between the small diametrical cylindrical neck portion and the cylindrical body portion with the shoulder portion having a domed curved face in the longitudinal section.
Alternatively, the small diametrical cylindrical portion manufacturing step of the method of the invention may be executed: such that at the small diametrical cylindrical portion shaping step, the bottomed cylindrical can is preliminary molded at its bottom corner portion into a He curved shoulder face of an arcuate longitudinal section and is then drawn at its bottom portion into a bottomed cylindrical portion of a smaller diameter than that of the body portion while the curved shoulder face of the bottom corner portion being unwrinkled by a pair of unwrinkling pusher and drawing dies having curved faces to contact closely with the curved shoulder face; such that after this, an unwrinkling pusher, which is provided at its leading end portion with a sloped face having a substantially straight longitudinal section approximating a tangential line drawn to an arcuate longitudinal section of a virtual curved face leading to a preformed curved shoulder face, a redrawing dies, which is positioned at a portion to face at least the pusher, which is provided at its leading end portion with a sloped face having a substantially straight longitudinal section approximating a tangential line drawn to an arcuate longitudinal section of a preformed curved shoulder face and which is provided at its portion on the leading end side from the sloped face with a bulging face having an arcuate longitudinal section, and a redrawing punch are used to perform one or more redrawing treatments for reducing the diameter of the bottomed cylindrical portion, while the bottom corner portion of the bottomed cylindrical portion of the small diameter formed by the drawing treatment being unwrinkled, thereby to shape the bottomed cylindrical portion of the small diameter into a radially small cylindrical portion of substantially the same diameter as that of the neck portion; and such that after this, one or two or more tapered faces formed between the small diametrical cylindrical portion and the curved shoulder face are extended and re-shaped into a smooth sloped face leading to the curved shoulder face by a pair of re-shaping tools having a surface shape of a straight longitudinal section approximating a tangential line drawn to a virtual curved face extending from the curved shoulder face, to form the shoulder portion shape into a smooth curved face of a straight longitudinal section leading to the curved shoulder face.
According to the bottle-shaped can manufacturing method of the invention, therefore, it is possible to manufacture the can which is decoratively printed at least on its body portion and which has the shoulder portion having the smooth curved face of the straight longitudinal section mainly.
On the other hand, the neck portion shaping step may be to curl the leading end portion of the small diametrical cylindrical portion opened, to form a curled portion and to thread the cylindrical portion below the leading end portion directly to form a thread.
According to the bottle-shaped can manufacturing method of the invention, therefore, the upper end of the neck portion is curled to provide a soft touch for the lips of a consumer when the consumer drinks the content directly from the neck portion of the bottle-shaped can. On the other hand, the neck portion is directly threaded to make the cost lower than the structure in which another threaded part is employed.
Alternatively, the neck portion shaping step may be to fit a cylindrical member of a resin threaded in advance, on the small diametrical cylindrical portion and to bend the leading end portion of the small m diametrical cylindrical portion opened, outward to bring the same into engagement with the cylindrical member of the resin.
According to the bottle-shaped can manufacturing method of the invention, therefore, the step of forming the threaded neck portion is simplified.